The present invention relates generally to data storage systems, and more particularly, to a method and architecture for optimizing the data zone on data storage disks employed in load/unload data storage systems.
A typical data storage system includes one or more data storage disks coaxially mounted on a hub of a spindle motor. The spindle motor rotates the disks at speeds typically on the order of several thousand revolutions-per-minute. Digital information, representing various types of data, is typically written to and read from the data storage disks by one or more transducers, or read/write heads, which are mounted to an actuator and passed over the surface of the rapidly rotating disks.
The actuator typically includes a plurality of outwardly extending arms with one or more transducers being mounted resiliently or rigidly on the extreme end of the arms. The actuator arms are interleaved into and out of the stack of rotating disks, typically by means of a coil assembly mounted to the actuator. The coil assembly generally interacts with a permanent magnet structure, and the application of current to the coil in one polarity causes the actuator arms and transducers to shift in one direction, while current of the opposite polarity shifts the actuator arms and transducers in an opposite direction.
In a typical digital data storage system, digital data is stored in the form of magnetic transitions on a series of concentric, closely spaced tracks comprising the surface of the magnetizable rigid data storage disks. The tracks are generally divided into a plurality of sectors, with each sector comprising a number of information fields. One of the information fields is typically designated for storing data, while other fields contain sector identification and synchronization information, for example. Data is transferred to, and retrieved from, specified track and sector locations by the transducers being shifted from track to track, typically under the control of a controller. The transducer assembly typically includes a read element and a write element. Other transducer assembly configurations incorporate a single transducer element used to write data to the disks and read data from the disks.
Writing data to a data storage disk generally involves passing a current through the write element of the transducer assembly to produce magnetic lines of flux which magnetize a specific location of the disk surface. Reading data from a specified disk location is typically accomplished by a read element of the transducer assembly sensing the magnetic field or flux lines emanating from the magnetized locations of the disk. As the read element passes over the rotating disk surface, the interaction between the read element and the magnetized locations on the disk surface results in the production of electrical pulses in the read element. The electrical pulses correspond to transitions in the magnetic field.
Conventional data storage systems generally employ a closed-loop servo control system for accurately and rapidly positioning the actuator and read/write transducers to specified data storage locations on the data storage disk. A servo writing procedure is typically employed to record servo information on the surface of one or more data storage disks comprising the data storage system during the manufacture of the data storage system. In accordance with a known servo information format, termed an embedded servo, servo information is written between the data storing sectors of each track. The servo data is thus embedded in the data storing tracks on each of the data storage disks, typically resulting in an alternating sequence of data and servo sectors comprising each track. In accordance with another known servo information format employed in data storage systems, termed a dedicated servo, the servo writer records servo information typically on only one of the data storage disks comprising the disk stack, and often on only one of the surfaces of the dedicated servo disk. The servo information stored on the dedicated servo disk is used to maintain accurate positioning and alignment of the read/write transducers associated with each of the data storage disks. During normal data storage system operation, a servo transducer, generally mounted proximate the read/write transducers, is typically employed to read the servo sector data for the purpose of locating specified track and data sector locations on the disk. It is noted that a servo sector typically contains a pattern of data bits, often termed a servo burst pattern, used to maintain optimum alignment of the read/write transducers over the centerline of a track when reading and writing data to specified data sectors on the track.
Turning now to FIG. 3, there is shown a prior art data storage disk 24 formatted in a conventional manner to include a data zone 73 biased toward, and registered with respect to, the inner diameter of the data storage disk 24. A traditional procedure for writing servo information to a data storage disk 24 includes establishing a data zone starting location 66 typically located near the central disk aperture 71. The innermost data track 64 of a conventional data storage disk 24 is generally situated proximate the clamp engagement surface 62 provided along the circumference of the central disk aperture 71. It is noted that the clamp engagement surface 62 represents a portion of the disk 24 surface area dedicated for clamping or mounting the disk 24 to the hub of a spindle motor (not shown) similar to a spindle motor 26 shown in FIG. 1. It is further noted that axial and radial clamping forces imparted to the disk 24 surface generally result in a high concentration of stress localized along the inner diameter of the disk 24, often resulting in some degree of disk surface distortion or curvature. Accordingly, the innermost data track 64 is generally spaced a short distance apart from the clamp engagement surface 62 to ensure a minimum level of data storage and data transfer reliability.
Having established a data zone starting location 66 and an innermost data track 64, often referred to as track zero, servo information is then transferred to the other disk locations to form a plurality of concentric data tracks 50 as shown in FIG. 1, defining the data zone 73. For example, after writing servo information to define the innermost data track 64, the servo writing transducer is moved a short distance away from the innermost data track 64 in a direction toward the outer periphery 67 of the data storage disk 24. A second concentric data track is then formatted on the disk 24, thereby leaving a narrow gap between the innermost data track 64 and the newly formatted data track. Formatting in this manner generally proceeds until an outermost data track 68 is defined. A data zone ending location 70 is generally defined to be the last data storage or servo sector location on the outermost data track 68.
In load/unload data storage systems, a load/unload ramp 60 is typically employed to engage a read/write transducer 27 assembly near the outer perimeter of the data storage disk 24 during periods in which the data storage system 20 is not in use. The transducer 27 is typically mounted to a slider body 63 to which a load tang 65 is affixed. During the power-down sequence of a load/unload data storage system 20 as shown in FIG. 1, the transducer 27 and slider body 63 assembly is lifted away from the surface of the data storage disk 24 by engagement between the load tang 65 and a load/unload ramp 60. It is generally understood that prolonged direct contact between the slider body 63 and the disk surface 24 results in an increase in static friction, commonly referred to as stiction, between the slider body 63 and disk surface 24. A high level of stiction between the slider body 63 and disk surface 24 is generally associated with excessive wear of the disk surface 24, and increased start-up current consumed by the spindle motor 26 to overcome the additional static friction. Unloading the transducer 27 and slider body 63 assembly from the disk surface 24 to the ramp 60 also reduces potential damage associated with short duration shock forces and other external forces imparted to the housing, (seen as housing 21 in FIG. 2), that, in turn, are transmitted to the sensitive components of the data storage system 20.
During the power-up sequence of the data storage system 20, the transducer 27 and slider body 63 assembly is loaded from the ramp 60 to the disk surface 24. As the rate of rotation of the spindle motor 26 increases, the airflow above the surface of the disk 24 results in the creation of an airbearing upon which the aerodynamic slider body 63 is supported, thus causing the transducer 27 and slider body 63 to rise a short distance above the disk surface 24. To facilitate unloading and loading of the transducer 27 and slider body 63 assembly to and from the ramp 60, a buffer region 72 is generally provided near the outer periphery 67 of the data storage disk 24. It is noted that the buffer region 72 of a conventional data storage disk 24 typically encompasses an appreciable amount of disk surface area that can otherwise be allocated for storing data.
Referring now to FIG. 4, there is shown a typical buffer region 72 of a conventional data storage disk 24. Among the various factors that influence the size of the buffer region 72, the mechanical tolerances associated with the fabrication of various data storage system components and the positioning of these components within the data storage system housing 21 during assembly are generally of particular concern. Each component typically has associated with it a maximum allowable tolerance with respect to the dimensions of the component and the positioning and orientation of the component within the data storage system housing 21. The buffer region 72 typically comprises an appreciable amount of disk surface area in order to accommodate the cumulative maximum or worst case tolerances of the components associated with unloading and loading the transducer 27 and slider body 63 assembly to and from the ramp 60.
Still referring to FIG. 4, there is shown a number of tolerance bands that contribute to the size of the buffer region 72 of a conventional data storage disk 24. Although the tolerance bands are presented merely for illustrative-purposes, the depiction in FIG. 4 demonstrates the aggregate effect of individual component fabrication and installation tolerances on the size of the buffer region 72. It is generally understood that in the design and manufacture of low cost, high volume data storage systems 20, it is common practice to allocate a buffer region 72 having a standard size for a family of data storage disks 24 and data storage systems 20. Although this standardization of the buffer region 72 across a family of disks 24 and systems 20 may advantageously simplify the manufacturing process, such standardization typically results in the allocation of an excessively large buffer region 72 for a particular data storage disk 24 and system 20, thereby reducing the disk surface area otherwise available for storing data, and the overall storage capacity of a data storage system 20.
Each of the tolerance bands comprising the buffer region 72 is representative of a portion of the disk 24 surface area required to accommodate the maximum or worst case manufacturing and assembly tolerance variations associated with a particular component of a data storage system 20. Tolerance band 74, for example, is illustrated as being representative of the outer diameter disk 24 surface area required to accommodate the maximum tolerance variations in the height and vertical positioning of the ramp 60 with respect to the substantially planar surface of the data storage disk 24. Manufacturing variations associated with the slope or incline of the ramp 60 are accommodated by an additional tolerance band 76. Further, variations in the mounting position of the ramp 60 on the housing base 22 are accommodated by another tolerance band 78.
Other mechanical and assembly tolerances which impact the size of the buffer region 72 include the configuration and orientation of the load tang 65 disposed on the slider body 63 which engages the ramp 60 when unloading and loading the transducer 27 and slider body 63 assembly to and from the disk surface 24. Variations in the tilt angle of the load tang 65 with respect to a plane defined by the surface of the disk 24 is accommodated, for example, by tolerance band 80. Height variations of the load tang 65 above the disk surface 24, by further example, are accommodated by an additional tolerance band 82. It is to be understood that other mechanical and assembly tolerances associated with the manufacture of data storage system components and the assembly of these components into the housing 21 also influence the size of the buffer region 72 of a conventional data storage disk 24.
An excessively large buffer region 72 negatively impacts both the data storage capacity and overall reliability of the data storage disk 24. It can be readily appreciated that allocating a larger amount of disk surface area for the buffer region 72 has the adverse effect of reducing the available disk surface area that can otherwise be dedicated for the storing of data. Further, it is generally understood by those skilled in the art that the data storage regions located near the outer diameter of the disk 24 provide for a significantly higher level of data storing and data transfer reliability, and a higher capacity for storing data, as compared to data storage regions located near the inner diameter of the disk 24. A data storage disk 24 formatted in accordance with a conventional servo writing procedure, as illustrated in FIG. 3, provides for a data zone 73 that is biased toward the inner diameter and, consequently, the relatively low reliability portions of the data storage disk 24. The necessity to allocate a sufficiently large buffer region 72 on a conventional data storage disk 24 to accommodate aggregate worst case component manufacturing and assembly tolerances, together with the conventional approach of biasing the data zone 73 toward the inner diameter of the disk 24, generally precludes the exploitation of the desirable outer diameter portions of the disk 24 for data storage purposes.
The present invention is a data zone optimization method and architecture for optimizing the orientation of the data zone on a data storage disk. The data zone is preferably biased toward the outer diameter of the disk, and is reference with respect to a data zone starting location established proximate a load/unload ramp. An optimum starting location for the data zone of a data storage disk is preferably determined by contacting the load/unload ramp with the transducer assembly, disengaging the transducer assembly from the ramp, and writing servo information indicative of the data zone starting location at a disk location proximate the ramp and transducer assembly contact point. Servo information indicative of the data zone is subsequently written to inner diameter disk locations with reference to the optimum data zone starting location on the outermost data track of the disk. The optimized data zone architecture may have either a predetermined or variable data storage capacity.